The proposed research represents an initial attempt to characterize interactions between the cerebellar cortex (CTX) and deep interpositus nucleus (INP) during rabbit eyeblink conditioning. Studies 1 and 2 will investigate whether CTX activity can influence the ability to make and learn conditioned responses. Rabbits will receive brief intracortical pulses of stimulation at different time points within paired conditioning trials, and the impact of these pulses will be analyzed. Study 1 will involve a within-subjects design, in which timing of stimulation will vary randomly between trials; analyses will reveal any stimulation timings that interfere with CR expression. Study 2 will use a between- subjects design, in which one group of rabbits will consistently receive stimulation shown to interfere with CR expression; analyses will reveal if particularly-timed CTX stimulation interferes with learning. Study 3 will examine whether or not INP-independent learning-related neural activity is seen in CTX. Trained rabbits will receive either neurotoxic INP lesions or sham lesions, after which single-unit activity from CTX cells will be recorded during additional training. Analysis will reveal whether CTX can sustain learning-related changes without the presence of the INP (and, thus, without CRs). Overall, these studies should add to our understanding of how parts of the cerebellar learning system interact to produce well-timed CRs.